this week I'm going to find out what ISO invariance is and whether or not it
makes a difference is OE basically refers to the voltage that runs across
the front of the sensor it's a standard that's been set by the international
standards organization hence the name is au the higher the voltage the greater
the amplification of the signal is from the sensor so in the simplest of terms
if you raise your ISO you can make your shutter speed faster and you can close
down your aperture if you lower your ISO you'll have to open up your aperture or
slow down your shutter speed to get the same exposure invariance basically means
there's no change along the scale so IR so in variants means there's no change
throughout the ISO on a certain parameter you don't need to know too
much about it as I've done a test to show you what I mean in practical terms
so if you are out at night shooting with an aperture f2 at a speed of 20 seconds
and an ISO of 6400 if you did exactly the same shot but with the ISO at 100
you could in theory bump the exposure back up and the image wouldn't look too
different now I want to test this and see how it works with my cameras the
only camera I have available that is ISO variant is the Canon 1300 D so I'm gonna
see what this one is like compared to my a 73 which I know is ISO invariant it's
not a fair comparison and they're very different cameras at very different
price points but that's not the point I'm making what I'm trying to show you
is the difference between a camera that is ISO invariant and one that isn't now
I'm trying to get my head around this and understand it as well and that's why
I'm making this video so I can have a much deeper understanding of ISO
invariance I kept the aperture as wide as possible and the shutter speed as
long as possible taking into consideration the 500 rule for the a 73
and the 300 rule for the Canon Sonne could go further and I have shot
with higher ISOs but I'm keeping them both at 6400 as this is the highest
amplified ISO that the Canon will go to I basically took seven images on the a
73 and seven images on the Canon 1300 D this is before I've processed them at
all this is ISO 100 200 400 800 1600 3200
6400 I shot all of these on the 25 millimeter batis at f/2 at 20 seconds
with a canon I used the samyang 24 millimeter F 1
point 4 even though it says 50 millimeters I think it does that with
these cameras whenever you put a manual lens on there with no electrical
connections so even though it says 50 millimeters it's not this is the 24
millimeter samyang at F 1.4 at 13 seconds so you at 24 millimeters have
followed the 300 rule and kept the exposure to 13 seconds any longer than
this and the stars will streak but I've got that extra light at F 1.4 over f2 so
with a Canon that's at 100 ISO 200 ISO 400 800 1600 3200 and 6400 now if I
switch over to the processed shots I haven't done much processing at all to
them all I've done is leveled out the exposures so they all sit at exactly the
same exposure so if we look at the Sony's this is ISO 100 200 400 800 1600
3200 and 6400 so you can see there's not that much difference between them and
this is because the a 73 is ISO invariant what you'll find is even if
you under expose the image with the ISO you can bring that image back later if
you want to have a play around with some of these images I've put a link in the
description so go to my website and there'll be a link there to down
load them now this is a one by one crop so it's really zooming in on the image
now if I go through them this is iso 100 iso 200 iso 400 iso 800 ISO 1600 ISO
3200 an ISO 6400 so you can see in the center of the frame there's not that
much difference at all and remember this shot at iso 100 has been pulled back in
lightroom by five stops and that's a massive amount now if we have a look at
the canons you can see it is au 100 when it's pulled back by five stops it is
really noisy and unusable you can see magentas and blues just horrible digital
noise so even when you zoom right out on the Canon and have a small image on the
screen you can still see this vertical noise whereas on the a7 three you can't
see the noise at all and it's a very usable image there was quite a lot of
dust where I was shooting and that's how you can see this darker patch on the
bottom of the image so it gets really dark and really underexposed so when i
zoom in on that bottom corner it is a little bit of noise but it's minimal and
remember this is the one at ISO 100 where I've changed by five stops of
Lights so that's a huge change in Lightroom with a very small loss in
image quality once you're up to ISO 400 the loss in quality is minimal now if we
look at the Canon in this area you can see the noise is very obvious even at
ISO 800 you can still see noise patterns there more so than the a 73 now this may
have something to do with it being a really cheap camera over an expensive
camera but also the Canon 5d Mark 3 and the 6d are both ISO variant so when you
pull them back this much in the darker areas you'll see a similar noise pattern
to the 1300 d saying that are used to shoot with a 5d Mark 3 and the 6d and
both of these when set properly could take some fantastic photos with
the canon 1300 d it did surprisingly well at the really high ISOs and for
such a cheap camera that's great you can get a really good camera that'll take
pictures of the stars for not much money at all but as we drop down and you can
see that noise creeping in when it's at ISO 400 brought back three stops it's
just about usable but if you zoom in you still get that noise pattern whereas
with the Sony a7 3 at ISO 100 the image is very usable and with some noise
reduction you'd even get rid of this noise pattern in the shadows so this
shows the invariance is in the noise after doing this test in the desert I
took a few different shots where I used light painting to brighten up the
foreground and shot one with a low ISO and the other with a high ISO and then
processed them in Lightroom now at a glance I can't really tell the
difference between these two shots the light painting is slightly different but
apart from that the sky looks almost identical when it comes to color
rendition and contrast they are very similar I thought the one with the
higher ISO would have less colors and less contrast but I can't distinguish
between the two again I've left a link in the
description to these shots so head over to my website where you can download
these images I have processed them and develop them as JPEGs but they're the
full size so you can have a look and see if you can spot any differences if you
do and you think one is better than the other let me know in the comments below
now in these astrophotography shots the colors don't vary that much so I went
down to the city and took some shots of cityscapes some with lower ISO s and
some with higher ISOs just to see how it effects the colors in
a cityscape I took a shot with ISO 100 and then another shot with ISO 12800
even though the second shot is noisier there's only a subtle difference in
color and contrast which are all things that you can correct in Lightroom which
is great because with these cameras you can now shoot at really high ISOs
without losing too much image quality at the max is a of 128 thousand there is a
lot of noise but I think this is because really high ISO s they amplify them
digitally and not electronically so from this I think the ISO invariance is
across the amplified ISO and not the digitally amplified higher so there's
basically three types of is a there's native ISO and this is the base is a
that has the best dynamic range colors and contrast then this amplified ISO
this is where the voltage is increased across the sensor which amplifies the
signal that comes from the sensor the third one is simulated is oh this is
above amplified ISO and it's when the signal is enhanced digitally and I think
with the Sony cameras this is when the image starts to get noisy in doing this
test it's made me think that we can use ISO invariants to our advantage the best
way to do this is when there are highlights that are overexposed in the
image then what I would do is underexposed the whole image exposing
just for the highlights then when I bring back up the exposure I know
there's not going to be too much noise if any in the shadows and there will
still be details in the highlights so those really bright highlights in
cityscapes won't be overexposed and blown out if you shoot with a different
brand and you're wondering whether your camera is ISO invariant or not I've put
a link to a list in the description below the main difference between a
camera that is ISO invariant and one that isn't seems to be the noise in an
ISO invariant camera you can under expose the shot and then bring it back
without any worries about there being too much noise in the image if your
camera isn't ISO invariant you'll have to get the ISO right in camera and
that's about it ISO invariance can definitely help your
photography and having a deeper understanding in it I know now that I
can push the limits further in taking a photograph as always if you like what
you see give me a thumbs up if you didn't give me a thumbs down and for
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